[Greenbuilding] ***SPAM*** Re: ***SPAM*** Re: r barrier recommendations

[Reuben Deumling]

On Tue, Jul 12, 2022 at 6:30 AM John Straube <jfstraube at gmail.com> wrote:

> You do need some lateral bracing in all buildings but esp in areas that
> might experience high winds and earthquakes. sheet wood is a very practical
> solution but overkill for a modest shop.  Wood sheet siding provides lots
> of lateral bracing (eg T-111 or SmartSide) but lap siding is not great. Let
> in diagonal 1x4 used to be used a lot.
>
Good point. I'll add that bracing. Thanks.

>
> Not sure what you mean by woven vs not woven. Polymer wraps are complex
> muliti-layer materials and come in many versions.

Kingsguard is a brand common around here: https://tinyurl.com/2p9cef8v

You should NOT use a perforated wrap or one that looks like landscape cloth
> (is that what you mean  by woven?). That said good long proven products
> like Typar and Tyvek are inexpensive (10 cents per square foot) and widely
> available and are absolutely sufficiently air and water tight.
>

I agree 10cents/SF is a great price. Around here it is closer to 25cents
though.

>
> Polymer underlayment are proliferating to replace #30 felt. Owens Corning
> ProArmor / GAF Dek-Armor etc are products that will work under metal roof
> and can be used over open joists with care and attention to detail.

Very helpful. Thanks!

> I doubt open rafters are recommended however, but I have seen it done.
>
> 12” gap is pretty good… getting to be almost like open. Sorry I thought
> you were planning smaller. Clearly, 0” is one extreme, and 2” is a bit
> better.  But it is sooo dependent on the soil, grading, snow piling, plants
> that can/do grow up around etc. If you get it to 18” and provide a open
> lattice skirt, it starts to behave like a floor over open air. But many
> unknowns.
> OTOH, if it is a shop, placing it on a gravel pad on insulation has
> benefits re rolling/driving carts and such in and out. But that is a
> project detail you would know about.
>
>
> > On Jul 12, 2022, at 08:56, Reuben Deumling <9watts at gmail.com> wrote:
> >
> > Thank you, John, for the detailed reply.
> > I have interspersed some comments below,
> >
> > On Tue, Jul 12, 2022 at 5:35 AM John Straube <jfstraube at gmail.com>
> wrote:
> > If you skip the plywood in OSP then you will need to use a standard
> membrain product such as Tyvek. Is there any reason you would not use the
> obvious?
> >
> > I am not using plywood chiefly because for buildings like this (style,
> size) I believe they have structurally done OK without it, and it hadn't
> occurred to me that plywood offered air sealing benefits sufficient to
> justify the effort/cost/etc.
> >
> > Also you were asking about the air barrier but really the most
> fundamental requirement of a shed or a hospital is rain control. Thus
> providing lapped housewrap under the siding and over the framing is
> fundamental and critical. Much more important than an air barrier.
> >
> > That is what I was originally intending to use, but when I looked more
> closely at those I realized they tend to be woven instead of continuous
> like tyvek (so expensive!) Which prompted my questions here. But if a woven
> house wrap product is suitable here I am happy to use it.
> >
> > We often call the rain control layer in a roof in a underlayment when it
> is placed below roofing that does not leak too much such as metal roofing
> and Ashfall shingles. You could use Tyvek for this as well but it is too
> slippery to work with and hence special grippier products are widely used.
> The benefit of large sheets of polymer are that they are strong enough and
> have few enough joints that you can tape them as an air barrier once you
> have properly gravity lap them for rain control.
> >
> > I have long used 30lb felt in this application but really don't care for
> its properties. I know there are fancier (special, grippier) products but
> have not yet investigated those.
> >
> > Providing air barrier continuity between the roof membrane which is
> above the framing and the wall membrane which is to the exterior of the
> framing is a bit more complicated but for a shed simply installing blocking
> and sealing with caulking around the edges should be sufficient.
> >
> > Thanks, that makes sense.
> >
> > There is no good answer for under your floor since what you are
> proposing is just considered "bad practice". That said I have several
> projects in my own property that to do some thing similar although they do
> provide at least 6 inches of clear air over the soil. These projects of
> mine are small 10' x 10' sized buildings that are not intended to be
> durable and in fact are likely to begin to have floor rot in 10 to 20 years
> of service. To locate a wood-based floor system directly on grade you would
> need to use something you probably don't like that is a foam plastic
> insulation on the underside of the wood protecting it from water vapour
> flow and keeping the framing at a different temperature than the grade. You
> will likely say you are not placing it on grade but you are clearly placing
> it so close to the grade it's almost the same.
> >
> > I am surprised that 12" (range currently is between 8" and 16"j is
> considered to be equivalent to placing it on grade. Are you saying the air
> gap + whatever
> > membrane would not offer meaningful protection for the wood over time?
> >
> > This one and a half or 2 inch foam layer underneath the wood will allow
> for a long term durable floor system. In your climate I would not bother
> putting fibrous insulation between the floor joists.
> >
> > I am open to foam. Had not considered it. I think I even have a stash of
> that stuff left over from another job. I take it you would suggest screwing
> the foam to the joists using those big plastic washers? And, presumably my
> method of building the floor sections upside down would be acceptable? I'd
> plan to keep the foam inboard of the sill plate.
> >
> > > On Jul 11, 2022, at 18:53, Reuben Deumling <9watts at gmail.com> wrote:
> > >
> > > Portland Oregon, dry hot summers; high humidity in the winter.
> > >
> > > I should have mentioned that I am skipping the plywood altogether. I
> am putting up rough sawn board-and-batten siding over the studs and
> blocking. My thought was to put that air barrier between those.
> > >
> > > On Mon, Jul 11, 2022 at 3:35 PM John Straube <jfstraube at gmail.com>
> wrote:
> > > Hey there Reuben.  A description of your climate would be helpful
> before I weigh in..
> > > In most cases taping up the plywood or osb sheathing would often be a
> great solution.
> > >
> > > On Mon., Jul. 11, 2022, 18:15 Reuben Deumling, <9watts at gmail.com>
> wrote:
> > > I hope there are still a few of you smart people out there. This list
> used to be so fun!
> > >
> > > I'm a little rusty on this stuff. So your thoughts are much
> appreciated.
> > >
> > > I am building a 250 sf shop in my back yard. I am insulating the floor
> right away (R19 FG batts) and the walls and 12/12 metal roof plane sometime
> in the future. My hope is to affix a barrier of some sort (6 mil plastic?)
> to the underside of the joists (ca. 12" unvented crawl space beneath), and
> wrap the walls and roof plane with some sort of air barrier, but am not
> sure what a good product choice would be for
> > > - under the floor
> > > - the walls
> > > - the roof
> > >
> > > Thanks for all suggestions.
> > >
> > > Reuben
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